fix: sync context progress bar with custom context length setting

- Add customMaxTokens override to ContextManager
- maxTokens is now derived from custom override or model default
- ChatWindow syncs settings.num_ctx to context manager
- Progress bar now shows custom context length when enabled

frontend/src/lib/components/chat/ChatWindow.svelte

@@ -182,6 +182,15 @@
 		}
 	});
 
+	// Sync custom context limit with settings
+	$effect(() => {
+		if (settingsState.useCustomParameters) {
+			contextManager.setCustomContextLimit(settingsState.num_ctx);
+		} else {
+			contextManager.setCustomContextLimit(null);
+		}
+	});
+
 	// Update context manager when messages change
 	$effect(() => {
 		contextManager.updateMessages(chatState.visibleMessages);

frontend/src/lib/memory/context-manager.svelte.ts

@@ -24,8 +24,14 @@ class ContextManager {
 	/** Current model name */
 	currentModel = $state<string>('');
 
-	/** Maximum context length for current model */
-	maxTokens = $state<number>(4096);
+	/** Maximum context length for current model (from model lookup) */
+	modelMaxTokens = $state<number>(4096);
+
+	/** Custom context limit override (from user settings) */
+	customMaxTokens = $state<number | null>(null);
+
+	/** Effective max tokens (custom override or model default) */
+	maxTokens = $derived(this.customMaxTokens ?? this.modelMaxTokens);
 
 	/**
 	 * Cached token estimates for messages (id -> estimate)
@@ -94,7 +100,15 @@ class ContextManager {
 	 */
 	setModel(modelName: string): void {
 		this.currentModel = modelName;
-		this.maxTokens = getModelContextLimit(modelName);
+		this.modelMaxTokens = getModelContextLimit(modelName);
+	}
+
+	/**
+	 * Set custom context limit override
+	 * Pass null to clear and use model default
+	 */
+	setCustomContextLimit(tokens: number | null): void {
+		this.customMaxTokens = tokens;
 	}
 
 	/**